I definitely lurked for a long time, first at TWoP then on LJ. Even once I got my LJ, I rarely commented for the first 3 or 4 months. I lurk(ed) because I'm terminally shy, and hate speaking up unless I know for sure that I'm welcome.

Same thing with commenting on fics - I read a lot of fic without saying anything, just because I don't like commenting in unknown spaces.